(1) Field of the Invention
The present invention relates to novel 1,4-dihydropyridine derivatives of the following general formula [I]: ##STR2## wherein R.sup.1 represents an alkyl group having from 1 to 4 carbon atoms or an alkoxyalkyl group having from 3 to 6 carbon atoms, R.sup.2 represents an alkyl group having from 1 to 8 carbon atoms, and A represents a hexamethylene group which may optionally be substituted by one or two alkyl groups having from 1 to 3 carbon atoms, which possess a hypotensive effect.
(2) Description of the Prior Art
Heretofore, there have been known, as 1,4-dihydropyridine derivatives, 4-(2-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid dimethyl ester (U.S. Pat. No. 3,644,627; hereinafter referred to as Nifedipine), 4-(3-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl ester 5-.beta.-(N-benzyl-N-methylamino)ethyl ester hydrochloride (Japanese Patent Publication No. 45075/1980; hereinafter referred to as Nicardipine) etc. which are useful as agents for improving the coronary circulation or the cerebral circulation. However, the vasodilating effect and the hypotensive effect resulting from said effect of these compounds have been reported to disappear within a short period of time, such as 30-40 minutes or so, at the effective intravenous dosage at which they become significant, for example, 10 .mu.g/kg, and also to be accompanied by a phenomenon of an increase in heart rate, which indicates one element to increase the burden on the function of the heart (Arzneimittel-Forschung, Vol. 22, No. 1, p. 33, 1972; ibid., Vol. 26, No. 12, p. 2172, 1976; Toho Igakukai Zasshi, Vol. 26, No. 2, p. 48, 1972). Therefore, when these compounds are to be employed as remedies for hypertention, cardiovascular diseases etc. which require continuous use of drug for a prolonged period of time, the improvement of the preparation, for example, by making it slow-releasing and the like, frequent administration which enhances the manifestation of side effects, or use in combination with other drugs is needed.